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7413 |
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Thursday, May 05, 2022, Hall D 9:40 AM Aviation Industry II |
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Solution precursor thermal spraying of gadolinium zirconate: Microstructural optimisation of GZ/YSZ thermal barrier coating |
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Kah Lok Leng* / University of Nottingham, Great Britain Acacio Rincon Romero / University of Nottingham, United Kingdom Federico Venturi/ Univeristy of Nottingham, United Kingdom Ifty Ahmed/ University of Nottingham, United Kingdom Tanvir Hussain/ University of Nottingham, United Kingdom |
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Although zirconia based ceramics, typically 7 – 8 wt.% Yttria Stabilized Zirconia (YSZ), is widely used as the ceramic topcoat for turbine blades, there is still a challenge of using YSZ beyond 1200°C. YSZ is well known to undergo a transformation from the metastable tetragonal phase (t’) into tetragonal (t) and cubic phases (c). These phase changes in YSZ beyond 1200°C are associated with 3 to 5% volume change in the microstructure, leading to coating failure. New materials and design for thermal barrier coatings (TBCs) to overcome the drawbacks of the current TBC are needed. One of the potential candidates to use as the future TBCs is gadolinium zirconate (GZ) that offers promising properties, such as, lower thermal conductivities, higher phase stabilities, better sintering resistance at elevated temperatures and better CMAS resistance; however, GZ cannot be used as a single layer TBC due to its low fracture toughness. To overcome the drawbacks of GZ, a double-layer approach has been proposed, by having GZ as the topcoat and YSZ as the second layer. In the proposed study, Solution Precursor (SSP) High Velocity Oxy-Fuel (SSP-HVOF) thermal spray was used to produce a double layer GZ/YSZ TBC and compared the thermal cycling performance with the single layer YSZ TBC. The thermal behaviour of the GZ solution precursor was studied, and the microstructure of the GZ layer was optimised. The porosity of the coating was tailored to improve the thermal cycling performance of the dense solution precursor coatings and the properties of the different coatings produced (i.e., thermal conductivity and fracture toughness) was analysed. |